SID-5 is an endosome-associated protein required for efficient systemic RNAi in C. elegans

Curr Biol. 2012 Oct 23;22(20):1938-43. doi: 10.1016/j.cub.2012.08.020. Epub 2012 Sep 13.


In the nematode C. elegans, RNAi silencing signals are efficiently taken up from the environment and transported between cells and tissues. Previous studies implicating endosomal proteins in systemic RNAi lack conclusive evidence. Here, we report the identification and characterization of SID-5, a C. elegans endosome-associated protein that is required for efficient systemic RNAi in response to both ingested and expressed double-stranded RNA (dsRNA). SID-5 is detected in cytoplasmic foci that partially colocalize with GFP fusions of late endosomal proteins RAB-7 and LMP-1. Furthermore, knockdown of various endosomal proteins similarly relocalizes both SID-5 and LMP-1::GFP. Consistent with a non-cell-autonomous function, intestine-specific SID-5 expression restored body wall muscle (bwm) target gene silencing in response to ingested dsRNA. Finally, we show that sid-5 is required for the previously described sid-1-independent transport of ingested RNAi triggers across the intestine. Together, these data demonstrate that an endosome-associated protein, SID-5, promotes the transport of RNAi silencing signals between cells. Furthermore, SID-5 acts differently than the previously described SID-1, SID-2, and SID-3 proteins, thus expanding the systemic RNAi pathway.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Biological Transport
  • Caenorhabditis elegans / genetics*
  • Caenorhabditis elegans / metabolism*
  • Caenorhabditis elegans Proteins / genetics
  • Caenorhabditis elegans Proteins / metabolism*
  • DNA / metabolism
  • Endosomes / genetics
  • Endosomes / metabolism
  • Green Fluorescent Proteins / genetics
  • Intestinal Mucosa / metabolism
  • Membrane Glycoproteins / genetics
  • Membrane Glycoproteins / metabolism*
  • RNA Interference*
  • RNA, Double-Stranded / metabolism
  • RNA, Small Cytoplasmic
  • Sequence Deletion
  • rab GTP-Binding Proteins / metabolism*


  • Caenorhabditis elegans Proteins
  • LMP-1 protein, C elegans
  • Membrane Glycoproteins
  • RNA, Double-Stranded
  • RNA, Small Cytoplasmic
  • Green Fluorescent Proteins
  • rab7 protein
  • DNA
  • rab GTP-Binding Proteins